This package introduces datatypes for typeclass-constrained effects,
as an alternative to monad-transformer based (datatype-constrained)
approach of multi-layered effects.
For more information, see the original paper at
http://okmij.org/ftp/Haskell/extensible/exteff.pdf.
Any help is appreciated!

Readme for extensible-effects-1.11.0.2

Advantages

Effects can be added, removed, and interwoven without changes to code not
dealing with those effects.

Disadvantages

For GHC version 7.8 and upwards

The extensibility comes at the cost of some ambiguity. Note, however, that
the extensibility can be traded back, but that detracts from some of the
advantages. For details see section 4.1 in the
paper. This issue
manifests itself in a few ways:

Common functions can't be grouped using typeclasses, e.g.
the ask and getState functions can't be grouped with some

class Get t a where
ask :: Member (t a) r => Eff r a

ask is inherently ambiguous, since the type signature only provides
a constraint on t, and nothing more. To specify fully, a parameter
involving the type t would need to be added, which would defeat the
point of having the grouping in the first place.

Code requires greater number of type annotations. For details see
#31.

Requires a Typeable instance on the return type. This is no longer a
limitation on GHC versions 7.8 and above.